docs: def user_to_rdf(user, graph=None):
      '''
      Map a Resource domain model to a DCAT/RDF graph
      '''
      graph = graph or Graph(namespace_manager=namespace_manager)
      if user.id:
          user_url = url_for('users.show_redirect',
                             user=user.id,
                             _external=True)
          id = URIRef(user_url)
      else:
          id = BNode()
      o = graph.resource(id)
      o.set(RDF.type, FOAF.Person)
      o.set(FOAF.name, Literal(user.fullname))
      o.set(RDFS.label, Literal(user.fullname))
      if user.website:
          o.set(FOAF.homepage, URIRef(user.website))
      return o